1. Field of the Invention
The present invention relates to a semiconductor laser device necessary for fiber optics communications, optical measuring systems, or optical information processing such as optical disks, and more particularly to a semiconductor laser device characterized by a channel portion and a current narrowing portion (that is, a channel structure).
2. Description of the Background Art
Semiconductor lasers require channel portions serving as a current narrowing structure to be fabricated in semiconductor. Such a structure includes a ridge structure. To form a ridge structure, it has been necessary to fabricate a striped pattern mask on a wafer, form a ridge structure portion by dry-etching or wet-etching, then perform a process operation of removing the pattern mask for etching, and thereafter perform crystal-growth of a current narrowing portion. Moreover, this method has inevitably increased the costs due to the channel forming operation and regrowth as wet-etching or dry-etching has been used. In addition, there have been problems such as characteristic variations between the steps and characteristic variations due to regrowth.
Structures different from the one described above includes a channel buried structure, in which a current narrowing layer is etched in a striped manner, followed by regrowth of a channel portion. In this case, the operation flow itself is similar to that in the ridge structure, thereby leading to the similar problems.
Still another structure includes a method of forming a channel by ion implantation. This structure has also required fabrication of a striped pattern mask, an operation of ion implantation, and a subsequent operation of removing the pattern mask. Moreover, this structure has increased the cost due to the channel forming operation and caused characteristic variations due to the variations between the steps.
Japanese Patent Laying-Open No. 7-263796 discloses a method of forming a channel portion using a substrate that is partially inclined. This structure has also required fabrication of a striped pattern mask on a wafer, etching of the substrate, and the subsequent operation of removing the pattern mask. Moreover, this structure has inevitably increased the costs resulting from the operations and increased variations between the steps, though there is no need for regrowth. In addition, since this structure has a non-flat crystal growth surface of a laser chip, there has been a need to correct inclination of laser light in packaging, which makes the packaging difficult.
Japanese Patent Laying-Open No. 10-107383 discloses a semiconductor laser device having a waveguide formed by crystal growth with light partially radiating on a substrate. The operation of forming and removing a pattern mask is not necessary in manufacturing this semiconductor laser device. A flat crystal growth layer, however, cannot be obtained since crystal is grown only on a light irradiated portion.
Japanese Patent Laying-Open No. 5-254984 discloses a method of forming a semiconductor thin film by applying high-power laser light on a substrate to melt the substrate and by causing the laser light to decompose and diffuse a dopant. Although this method also requires no operation of forming and removing a pattern mask, a flat crystal growth layer cannot be obtained.
Japanese Patent Laying-Open No. 5-144744 discloses a method of forming a semiconductor thin film by introducing a doping gas material while applying laser light on a substrate to form a temperature distribution. In this forming method, however, there is no specific description as to what range on the substrate should be irradiated with laser light and how the resultant semiconductor device is structured.